Punch press die



Oct. 3, 1944 E. H. RUDER 2 359 682 Filed Jan 1 1944 FIG \\ if HmPatented Oct. 3, 1944 PUNCH PRESS DEE Edward H. Ruder, Ferguson, Mo.,assignor to Curtiss-Wright Corporation, a corporation of DelawareApplication January 11, 1944, Serial No. 517,889

4 Claims.

This invention relates to punch presses and more particularly isconcerned with improvements in the dies employed in connection with suchpresses.

In order to insure proper cooperation between the die elements of apress of the type referred to, it is necessary, and also the practice,to so design the said elements that there will be a predeterminedclearance between their cooperating cutting edges. Such clearance servesthree purposes. It reduces the power required to operate the press itpromotes a smooth shearin action; and it prevents actual contact betweenthe cooperating edges of the die elements and hence avoids nicking andbreaking such edges. The amount ofv clearance is dependent principallyupon th gauge of the stock and its composition.

In the fabrication of a modern airplane it is not unusual to employseveral hundred thousand rivets, thereby necessitating the formation ofover half amillion holes in the parts to be riveted, in addition to theusual number of bolt and pilot holes. The formation of rivet, and other,holes in such large numbers has presented one of the major problems inthe mass production of aircraft. Heretofore, it has been proposed toutilize steel perforating dies for punching the rivet holes in order toincrease production. Such dies afford an ideal solution to the problemof forming rivet holes, as they may be employed to punch simul- Itaneously all the holes in a part, regardless of the pattern, spacingand size of such holes. However, apart from requiring the use ofmaterials, now considered critical, the employment of perforating dieshas had the objection that their manufacture has necessitated theexercise of a high degree of skill in order to obtain proper alignmentof the cooperating die elements.

One object of the present invention, therefore; is to overcome the aboveobjection, this object contemplating a punch element which is so formedthat it will enable the production of dies, comparable in action tosteel dies, from inexpensive, non-critical materials and without theexercise of a high degree of skill.

A further object is to provide a die element which is so designed thatits alignment with a companion elementmay be effected rapidly,accurately and without the aid of special tools,

The invention is illustrated in the accompanying drawing, in which:

Figure l is a perspective View, partially in section, of a punch presshaving die elements embodying the features of the invention.

Figure 2 is a fragmentary, sectional view through companion die elementswhich are shown in the relative positions in which the are supportedwhile the punch element is being mounted in its pad.

Figure 3 is a generally similar sectional view with the die elementsshown in connection witha sheet of stock and in the relative positionswhich they occupy upon completion of a punching operation.

Figure 4 is a detail section taken along line 44 of Figure 2.

Although the die elements of the invention are not necessarily solimited in use, they may be employed to particular advantage asperforating dies and are so illustrated in connection with a subpresswhich, as shown in Figure 1, comprises upper and lower bolster plates I0and II, respectively, the former being movably mounted on guide rods I2which are carried by the bolster plate II and being adapted to beactuated by a principal press in accordance with conventional practice.A punch pad I3, which may be of Masonite or the like, is secured to theupper bolster plate by bolts I4 while a die pad I 5 of similar materialis secured to the lower bolster plate by similar bolts I6. Mounting ofthe punch and die pads upon their respective bolster plates ispreferably accomplished with the aid of line-up bushings ll. The latterare recessed to accommodate the heads of the bolts and may be anchoredin the pads by Cerromatrix, 2. bismuth-lead-tin-antimony alloy whichmelts at a temperature of the order of 245 F., or a similar alloy.

Cooperating punch and die elements are indicated at IB and I9,respectively. The said elements may be of any desired number and sizeand may be arranged in any desired spacing and pattern. They may eitherperforate, or otherwise deform, the stock material to be acted upon. Thepunch element I8 is preferably anchored in the pad I3 by a filling 20 ofCerromatrix 01' the like While the die element I9 is anchored in the padI5 by a similar fillin 2|, it being noted that the line-up bushings I1employed in connection with the die pad I5 and the die elements I9support the die pad in spaced relation with respect to the upper surfaceof the lower bolster plate and that the extension of the die element iscut away at opposite sides to form openings '22. Provision is thus madefor permitting the escape from the die elements of the slugs produced inthe punching operation. I 7

Referring to Figure 3, it will be noted that the parts of the press areshown in the positions they occupy upon completion of a punchingoperation, the stock in which the hole is formed in such operation beingindicated at 23 and the slug 'produced at 24. In accordance with theinvention the punch element I8 is formed between its tip portion 25 andshank portion with a guide section 26, the diameter of the tip portionbeing predetermined so that its cutting edge will be suitably smaller indiameter than, and hence have the proper clearance with respect to, thecutting edge provided by the lip portion 21 of the die element I9. Thediameter of the guide section 26 of the punch, on the other hand, is ofsubstantially the same diameter as the diameter of the cutting edge onthe die element and is so formed that the guide section 26 will enterthe die element I 9 with a relatively tight sliding fit. The differencein diameter between the tip portion and guide section of the punchelement is, it is noted, exaggerated for the purpose of clarity. Thepunch described has the advantage that it enables the die elements to beaccurately aligned with respect to one another in their respective padsto thereby insure a predetermined uniform clearance between the cuttingedges of the said elements, such alignment being effected in theoperation in which the punch elements are mounted in the punch pad.

After the die elements I9 have been mounted in the pad I5, the latter isupported in the position shown in Figure 2 and the punch elements I9are inserted into the companion die elements, the guide sections 26 ofthe punch elements being caused to enter the die bores as shown inFigure 2. The punch pad, in which suitable openings have been previouslydrilled, is then arranged over the punch elements and upon the die pad,a sheet of paper 28 preferably being first placed upon the die pad.Thereafter the molten material which i to form the fillings 20 is:poured into the openings around the punches and in the openings aroundthe bushings I! and permitted to solidify, the paper 28 preventing themolten material from flowing onto the die pad.

To attach the pads I3 and I5 to the upper and lower bolster plates Inand I I, respectively, of the subpress so that the punch and dieelements Will be properly aligned, it is only necessary, assuming thelower pad has been secured to the lower bolster plate by the bolts I6and the upper pad to be arranged upon the lower pad with the guideportions 26 of the punch elements occupying the openings in the dieelements I9, to lower the upper bolster plate upon the upper pad, drillholes through it into the upper pad and insert suitable dowel lpins.Thereafter the upper bolster plate may be elevated and, while utilizingthe dowel pins to hold the upper pad in the proper position, be drilledand the inner ends of the holes threaded to receive the bolts I 4 whichmay thereupon be inserted and tightened.

From the foregoing it will be apparent that as the guide sections 26 ofthe punches are coaxial with respect to the tip portions and have arelatively tight fit in the die bores, the cutting edges of the puncheswill beheld in concentric relation with respect to the cutting edges ofthe dies. This relation will be maintained in the operation of thepress, it being understood that in such operation the movement of thepunch pad toward the die pad is terminated before the guide sections ofthe punches enter the bores of the companion dies. The constructiondescribed has the advantage that the clearance which may bepredetermined in any particular instance to insure the best performanceof the press will be uniform with respect to the die elements of eachpair.

It will be noted that in the punching operations the vertical thrustswhich are developed are transmitted substantially wholly through thepunch and die elements, the Masonite pads and fillings I1, 20 and 2Iserving merely to hold and guide the said elements and to prevent theirlatera1 displacement. The use of Masonite or similar material for thepunch and die pads has the advantage that mounting and alignment of thepunch and die elements are greatly facilitated. The pads may be readilyformed with the necessary openings and, as the latter are considerablyoversize with respect to the elements for which they are formed, anynecessity for drilling such opening with a high degree of accuracy isavoided.

The feature of the invention are not necessarily limited to use inconnection with die elements for producing rivet holes but may beemployed to equal advantage in connection with die elements of variousshapes and sizes and for various purposes. In the event that any of thedie elements should be broken, or otherwise become unsuitable for thepurpose in view, such elements may be readily removed and, be replacedby melting out the filling material which holds them in place, if in anisolated position, or drilled out if located in a confined area in whichthe use of heat might loosen adjacent punches. In the event that aparticular assembly should become obsolete, the die elements, bushingsand filler material may be readily reclaimed for further use as theywill not be damaged or impaired by the heat required to melt the fillermaterial.

I claim as my invention:

1. A punch element adapted to be carried by a holder and having a tipwhich may be caused to enter a die opening in a companion element whichis adapted to be carried by a cooperating holder, the tip of said punchelement and said companion element being formed with coacting; annularworking edges designed to have a predetermined, over-all workingclearance and said punch element also being formed with an integralannular guide portion which is located behind said tip and which may becaused to enterthe'i die openin in said companion element to establishand maintain said working clearance while said elements are beingattached to said holders, the working edge and guide portion of saidpunch element having a difference in diameter correspondingsubstantially to said clearance.

2. A punch element adapted to be carried by a holder and to be moved bythe latter into a die opening in a companion element which is adapted tobe carried by a cooperating holder, said elements being formed withcoacting working edges designed to have a predetermined, over-allworking clearance and said :punch element being also formed behind itsworking edge with a guide portion which may be caused to enter andoccupy the die opening in said companion element to establish andmaintain said working clearance while said elements are being attachedto said holders.

3. A punch element adapted to'be carried bya holder and to be moved bythe latter into a die opening in a companion element which is adapted tobe carried by a cooperating holder, said elements being formed withcoacting, annular cutting edges designed to have.a.predetermined,over-all working clearance and said punch element bein also formedbehind itsworking edge being formed with coacting, annular cutting edgesdesigned to have a predetermined, over-all working clearance and saidpunch being also formed behind its working edge with a guide portionwhich is cooperable with said die to establish said Working clearancewhile said punch is being attached to said holder, the working edge andguide portion of said punch having a difference in diametercorresponding substantially to said clear- 10 ance EDWARD H. RUDER.

